1. Field of the Invention
This invention relates to the structure of a hydrant and particularly to a anti-freezing hydrant.
2. Description of Related Art
Refer to FIG. 1 as an exploded view illustrating the appearance of a conventional anti-freezing hydrant. The anti-freezing hydrant 10 mainly comprises an outer tube 11; one end of the outer tube 11 is provided with a water inlet 111 and the other end is provided with a joint port 112 and a water outlet 113. A handle knob 12 and a valve 13 are assembled in the joint port 112. The handle knob 12 is assembled onto the joint port 112 and may revolve the valve 13 to valve the water inlet 111 or the water outlet 113. In order to follow the standard of ASSE-1019A, refer to FIG. 2. A back pressure valve 14 is provided in the valve 13 for water to flow from the water inlet 111 in a single way. Further, the handle knob 12 is provided with a hollow valve rod 121 of which an end is provided with a lump 122 on which a water leakage hole 123 is formed. Here, a back pressure device 15 is provided between the handle knob 12 and the valve 13 and comprises a back pressure stopper 151 and an elastic component 152. With the bounce effect applied by the elastic component 152, the back pressure stopper 151 stops the water leakage hole 123 of the lump 122, and a gum ring is adhered to a side of the stopper 151 to seal the hole 123. When water is led into the water outlet 113 due to siphonage, the back pressure stopper 151 draws back because of the pressure of water; the gum coil 153 cannot stop the water leakage hole 123 so that water may be led into the valve rod 121 from the water leakage hole 123 and thus leaks out of the handle knob 12, thereby a warning being given. For use, the gum ring 153 is adhered onto the back pressure stopper 151 but easily falls off and gets aging after being used, thereby failing and causing the water leakage hole 123 to give an erroneous warning. The water leakage hole 123 is designed in the manner of inclined plane machining and is not easily processed. Next, the back pressure valve 14 stops water by using an O-shaped ring 141. The O-shaped ring 141 is subject to and blocked with foreign matters and thus cannot fully block water, thereby providing poor effect of leakage blocking.
Consequently, because of the technical defects of described above, the applicant keeps on carving unflaggingly through wholehearted experience and research to develop the present invention, which can effectively improve the defects described above.